As where the drawer of a bill of exchange, knowing that time had been given by the holder to the acceptor, but supposing held in Massachusetts, that a promise to pay under mistake of law is not binding. May v. Coffin, 4 Mass. 346; Warder v. Tucker, 7 Mass. 452; Freeman v. Boynton, 7 Mass. 488. See also Haven v. Foster, 9 Pick. 112, where the question is ably argued by counsel, and all the authorities bearing upon the question cited; Lanning v. Carpenter, 48 N. Y. 408 (1872); Pitcher v. Hennesey, lb. 415.

Although the general doctrine, as stated in the text, seems justified upon the ground of public policy; yet so arbitrary a rule, founded upon so harsh a presumption, should be modified by every exception which can be introduced without negativing its effect. And it would, as we think, be more coincident with justice, and better recommended to common sense, if an exception to the rule should be introduced in respect to promises of payment made upon a mistaken supposition of liability, or actual payments made under the same circumstances, when there was neither a moral, nor legal obligation to support them. Indeed, the doctrine as stated by Lord Mansfield in Bize v. Dickason, 1 T. R. 285, and cited in the beginning of this note, and which was subsequently reaffirmed by him in Ancher v. Bank of England, 2 Doug. 637, seems to us to be the most equitable doctrine.

If there be, at the time that a contract is entered into, a mistake of the law applicable thereto, which entirely modifies it, to enforce such an agreement is to create a new contract, which was never assented to understandingly, and to impose duties and liabilities which the party never contemplated assuming. So, also, if there be a promise, or an actual performance of a contract, upon the supposition of liability, that liability becomes the very basis of the contract, and its non-existence being an utter failure of consideration, an executory or executed contract founded thereupon would, by one of the first principles relating to contracts, be wholly void. If money be paid away when it is not honestly due, the law, in refusing relief, allows the party receiving payment to take advantage of a mistake, made conscientiously and without negligence, and thereby to defraud the party making such payment. Besides this, a payment without consideration does not divest the property from the payer, and the payee, upon principle, becomes his bailee or trustee, and ought to be liable to an action of trover for a tortious conversion, unless he deliver it up. This arbitrary rule only destroys the remedy without affecting the right.

Besides, where money has been paid upon a mistake of law, or where a promise has been made upon a sup'posed liability, it is as much a mistake of fact as of law. The liability or non-liability of any person is a plain fact, founded, to be sure, upon a legal principle, but still a fact independent of it, about which any one may be mistaken. And even if this be not so, why should not a man be allowed to recover money paid upon a mistaken belief of liability, when his mistake has formed the basis of his contract, and injuriously affected his rights, and when, without such mistake, the other party would have no claim upon him ? It is not only unjust to the party.

1 Leslie v. Baillie, 2 Younge & Coll. C. C. 91, 96, 97. See Stevens v. Lynch, 12 East, 38. But see contra, Warder v. Tucker, 7 Mass. 449; May v. Coffin, 4 Mass. 347; and Logan v. Mathews, 6 Barr, 417.

2 Strohecker v. Farmers' Bank, 6 Barr, 41.

3 Coolidge v. Brigham, 1 Met. 551; Allen v. Hammond, 11 Peters, 63 Story on Sales, § 367, and cases cited; post, § 1062.

4 Veazie v. Williams, 3 Story, 628.

dred pounds, avoirdupois weight, should constitute a ton, but supposed that a ton was to be reckoned at twenty-two hundred and forty pounds, gross weight; it was held, that the ignorance of the statute law on the part of the complainant furnished no sufficient ground to reform the contract.1

§ 527. The citizens of one country are not presumed to know the laws of a foreign country, and ignorance or mistake with regard to them is considered as a mistake of fact, and not of law. In this respect, the laws of each of the different States in America are foreign laws, of which the citizens of all the others are presumed not to be cognizant.2